As regenerative refrigerating apparatus used as a compact and cryogenic refrigerating apparatus, refrigerating apparatuses presenting various levels of the performance have been developed up to now, and the regenerative refrigerating apparatus has development history exemplified by a Stirling refrigerating apparatus, a GM refrigerating apparatus, and further, a pulse tube refrigerating apparatus. All of these refrigerating apparatuses employ a method of compressing and expanding working gas serving as refrigerant in the apparatus, thereby generating cool and heat, and the GM refrigerating apparatus and the pulse tube refrigerating apparatus have been generally used recently.
Particularly, since the pulse tube refrigerating apparatus has a simple structure which does not have a moving part in a low temperature section as shown in FIG. 2 described later, it hardly generates vibration at the low temperature section, and thus presents a high reliability for a long term operation. Further, since maintenance-free may be expected for the operation of the pulse tube refrigerating apparatus, the pulse tube refrigerating apparatus plays an important role as cooling means for sensors and semiconductor manufacturing apparatuses.
FIG. 1 shows a schematic diagram describing the basic constitution and operation principle of the GM refrigerating apparatus. In an expanding/compressing unit 1, a displacer 1c is provided as an expansion piston, and the displacer 1c is constituted so as to be reciprocated by a stepping motor during the operation. A room temperature end 1a is disposed at the top end of the expanding/compressing unit 1, and a low temperature end 1b is disposed at the bottom end on the opposite side. Similarly, a regenerating unit 2 is constituted as a cylindrical tube body including a room temperature end 2a at the top end, and a low temperature end 2b at the bottom end, and is filled with a stacked regenerating material such as stainless steel mesh inside. Further, a connecting tube 3 is provided between the low temperature end 1b of the expanding/compressing unit 1 and the low temperature end 2b of the regenerating unit 2 for connecting them with each other.
Pressure control means 4 is comprised of a compressor 4a, a high pressure selector valve 4b, and a low pressure selector valve 4c, and the high pressure selector valve 4b, and the low pressure selector valve 4c are in synchronism with the movement of the displacer 1c. When the displacer 1c is on the bottom end side of the expanding/compressing unit 1, the high pressure selector valve 4b opens, and high pressure working gas flows into a top space of the displacer 1c. Then, when the displacer 1c moves up to the room temperature end 1a, the high pressure gas in the top space moves to a bottom space while the gas is being cooled passing through the regenerating unit 2. In this state, since the bottom section is at a low temperature, the gas contracts, and the high pressure working gas is supplied from the high pressure selector valve 4b. When the displacer 1c moves to the top end side, the high pressure selector valve 4b closes, and the low pressure selector valve 4c opens to discharge the high pressure gas in the low temperature space. As a result, the gas expands adiabatically, and thus, cool is obtained in the bottom space at the low temperature end 1b. When the displacer 1c goes down to the bottom end side while the low pressure selector valve 4c is open, the low temperature gas in the low temperature space absorbs refrigerating load, and moves to the top space while being heated passing through the regenerating unit 2, and remaining gas returns to and sucked by the pressure control means 4. When the displacer 1c goes down to the low temperature end 1b, the high pressure selector valve 4b opens, and high pressure working gas flows into the top space of the displacer 1c. 
The cold obtained at the low temperature end 1b of the expanding/compressing unit 1 is heat-transferred to a subject to be cooled 7 through a cold head (cooling unit) 6 covering the low temperature end 2b of the regenerating unit 2 and the low temperature end 1b of the expanding/compressing unit 1. As described above, since the GM refrigerating apparatus has the structure presenting the reciprocating motion by the stepping motor, vibration tends to occur on the expanding/compressing unit 1, and the vibration may be transferred to the subject to be cooled 7 through the cold head 6 as a medium.
FIG. 2 shows a schematic diagram describing the basic constitution and operation principle of the pulse tube refrigerating apparatus. The pulse tube refrigerating apparatus is constituted by removing the displacer in the GM refrigerating apparatus, and is comprised of a single tube body, thus replacing working gas by phase difference. Consequently, the number of parts of the refrigerating apparatus is small, and the structure is simple.
As shown in the drawing, the pulse tube refrigerating apparatus is constituted as a pulse tube 1 including a room temperature end 1a at the top end, and a low temperature end 1b at the bottom end, and similarly, and a regenerator 2 including a room temperature end 2a at the top end, and a low temperature end 2b at the bottom end, and filled with a stacked regenerating material such as stainless steel mesh inside.
The pressure control means 4 communicating with the room temperature end 2a of the regenerator 2, and oscillating the pressure of working gas is comprised of a compressor 4a, a high pressure selector valve 4b and a low pressure selector valve 4c. The phase control means 5 which communicates with the room temperature end 1a of the pulse tube 1 so as to adjust the phase difference between the pressure fluctuation and the position fluctuation of the working gas in the refrigerating apparatus is usually provided with a buffer tank. When the refrigerating apparatus is operating, since the working gas in the apparatus and the working gas in the buffer tank communicate with each other, and the phase difference between the pressure fluctuation and the position fluctuation of the working gas is generated by a certain flow resistance, controlling this phase difference adiabatically expands the working gas in a neighborhood of the low temperature end 1b of the pulse tube 1 so as to generate cold.
The low temperature end 2b of the regenerator 2 and the low temperature end 1b of the pulse tube 1 are connected with each other by a connecting tube 3. The cold obtained by the low temperature end 1b of the pulse tube 1 is heat-transferred to a subject to be cooled 7 through a cold head 6 covering the low temperature end 2b of the regenerator 2 and the low temperature end 1b of the pulse tube 1 as in the case of the GM refrigerating apparatus.
As shown in FIGS. 1 and 2, the cooling in the conventional GM refrigerating apparatus and pulse tube refrigerating apparatus is structured such that the cold head covering the cold generating section is provided, and is brought in contact with the subject to be cooled to transfer the cold. As a result, the cold head uniformly constituted with copper having high heat conductivity is employed for causing efficient heat transfer.